As you will see, on
the Warwick Archipelago, the founding population will diversify into several distinct
species in a manner consistent with the adaptive radiation history of the Hawaiian
honeycreepers and similar groups elsewhere in the world. The diversity of habitat
on the islands in this archipelago provides more opportunity for divergence than does
the less diverse mainland. Also, the distance from the mainland makes immigration
difficult, leaving dozens of niches available when the pollenpeepers arrive. Follow
along to explore what happens to the Warwick Archipelago pollenpeepers.

Warwick Archipelago: 5 Million Years Ago

Highlight

Nearly 150 pollenpeepers arrive on largest island.

Pollenpeeper changes

As the hurricane loses its intensity, nearly 150
pollenpeepers are carried by the storm to the largest island of the Warwick
Archipelago, an island chain 600 miles northeast of the mainland.

The group settles on the north side of the island,
where the habitat is most similar to the pollenpeepers' mainland home.

Habitat

A very high ridge divides the large island the pollenpeepers
now occupy.

The north side of the island has a lush, wet habitat on the
coast; the island's south side is desertlike, receiving less than half the
rainfall of the north side.

Food

Seeds

Many seeds available

Insects

Few insects available

Flowers

No nectar flowers available

Competition

There is virtually no competition for the new immigrants
when they arrive on the island. The only other bird on the archipelago is a
species of hummingbird that lives in the high alpine forest of another island
in the Warwick chain.

Predators

Very few predators threaten these pollenpeepers

Warwick Archipelago: 4 Million Years Ago

Highlight

The population grows quickly and pollenpeepers begin dispersing.

Pollenpeeper changes

The population on the north side of the largest island
grows gradually.

Dispersal from the large island to other islands in the
chain is rare, though, due to the low population density on the large
island, the small size of other islands in the chain, and the distance between
the islands.

There is very little change in the appearance of
pollenpeepers on the island chain.

Habitat

Initially, the pollenpeepers settle along the coast of each
island -- the coastal habitat is most like that of their original mainland home.

As individual populations grow, small groups expand their
ranges, dispersing slowly into other areas.

Food

Seeds

Many seeds available

Insects

Some insects available

Flowers

Few nectar flowers available

Competition

There is very little competition among pollenpeepers. When
competition does arise, some members of the population move to another area or
to a slightly different habitat.

Predators

Very few predators threaten these pollenpeepers

Warwick Archipelago: 3 Million Years Ago

Highlight

Isolation on high mountains causes rapid change in one
population.

Pollenpeeper changes

The first pollenpeeper group to become significantly
isolated and differentiated from the others is a population occupying the
highest alpine mountains of one of the middle islands in the chain.

Habitat

The alpine mountain habitat of the newly isolated population
is very high, cool, and wet, with a short growing season. Flowers are plentiful
seasonally, offering pollen and nectar to insects and birds.

Food

Seeds

Some seeds available

Insects

Some insects available

Flowers

Some nectar flowers available

Competition

Competition among different populations of pollenpeepers
remains low throughout the archipelago.

Predators

Very few predators threaten these pollenpeepers

Warwick Archipelago: 2 Million Years Ago

Highlight

Populations diversify rapidly in response to new conditions.

Pollenpeeper changes

Populations of pollenpeepers become established and relatively
isolated in each of the archipelago habitat types: coastal scrub, desert, lowland
forest, and high alpine forest.

Desert pollenpeepers develop short, wide beaks similar
to those of the coastal birds. Their plumage, however, begins to distinguish them
from the coastal birds: Both males and females begin to show dramatic red, yellow,
and black plumage.

Lowland forest pollenpeepers develop beaks specialized for
picking insects out of tree bark. Their feet and tails become well adapted to
this type of foraging, too, allowing them to cling to the trunks of trees. Both males
and females develop very dark body plumage, accented by brilliant white wing patches.
Some males begin to show the beginnings of a red head crest, which females highly
prefer.

The beaks of alpine forest pollenpeepers become longer and
narrower, allowing the birds to probe inside flowers for insects and, increasingly,
flower nectar. The plumage of the males is becoming a brilliant iridescent green.

Habitat

The island chain continues to offer an extremely diverse set
of habitats, from low, dry desert to high-elevation alpine forest. Each habitat
type has its own best food source for pollenpeepers.

Food

Seeds

Many seeds available

Insects

Many insects available

Flowers

Many nectar flowers available

Competition

Not long after the pollenpeepers arrived on the archipelago,
there were countless available habitats for groups to move into when competition
in a preferred habitat got too intense. Now, available niches are dwindling.

Predators

Very few predators threaten these pollenpeepers

Warwick Archipelago: 1 Million Years Ago

Highlight

Lowland forest population begins feeding on nectar.

Pollenpeeper changes

Coastal pollenpeepers specialize in cracking the shells of
seeds quickly and efficiently using their wide, heavy beaks.

The beaks of desert pollenpeepers look very much like those
of the coastal birds, only slightly heavier and shorter. The desert birds,
however, distinguish themselves with their flashy yellow, red, and black
plumage.

Lowland forest pollenpeepers develop a long, sharp, and
slightly down-curved beak that allows them to most efficiently find and
retrieve beetle larvae and moths under the bark of trees. This beak also allows
the birds to feed on flower nectar where flowers are plentiful. Their plumage
becomes darker, except for the brilliant white wing patches and the males' red
crest.

Alpine forest pollenpeepers do well with their long, sharp,
sickle-shaped beak. It is perfectly suited for obtaining nourishment
from one of the island's most plentiful flowers, a relative of the hibiscus that
hides its nectar deep within curved, tubular flowers. The brilliant iridescent
green of the males is also highly selected by females; over successive generations,
it becomes more intense.

Some of the lowland forest pollenpeepers expand their range to
higher elevations as their preferred habitat creeps higher. They are
different enough in color and size from other pollenpeepers that as
they encounter alpine forest pollenpeepers, they do not interbreed with them.
They do, however, compete with them for food.

Habitat

A climate change on one of the islands causes the boundary
between two populations' habitats to shift. Shrubs from the lowlands encroach on
and out-compete some of the lowermost alpine forests, resulting in a replacement
and mixing of habitat types.

Food

Seeds

Many seeds available

Insects

Many insects available

Flowers

Many nectar flowers available

Competition

As lowland forest pollenpeepers expand into the habitat of
the alpine pollenpeepers, the two populations begin competing with one another.
Lowland forest birds now feed preferentially on nectar in this habitat.

Predators

Very few predators threaten these pollenpeepers

Warwick Archipelago: Present

Highlight

Six distinct populations occupy the archipelago.

Pollenpeeper changes

There are now six distinct populations of pollenpeepers
on the archipelago and four clearly defined species. The four species have
become specialized in the way they find food and other resources. They are now
genetically isolated from one another, meaning that they do not interbreed
successfully with any of the other species. The distinct populations that are not
yet distinct species continue to diversify from one another and will likely soon
be.

The pollenpeepers that most recently moved from the
lowland forest into alpine pollenpeeper habitat maintain a tenuous hold on
survival given the competition of the more established birds. In response
to the competition, both the newest arrivals and alpine species are diverging
further from one another, eliminating overlap in their behaviors and the resources
they use.

Alpine birds now have extremely long down-curved beaks,
which allow them to obtain nectar from the deepest flowers -- an adaptation
they did not have before the birds from the lowland forest arrived.

The new arrivals from the lowland still feed on flower nectar
they can reach with their relatively short beaks. These flowers contain less
nectar than the deeper flowers, but they also attract pollinating insects,
for which the lowland birds have no competition.

A portion of the desert population occupying the east end
of the archipelago moves to a new island that has formed. They are best suited
to the hot, dry, sparsely vegetated environment they encounter there.

Habitat

A new island has formed on the east end of the archipelago.
For several hundred years, the island sits quietly barren. Periodically seeds
are carried ashore by pollenpeepers and ocean currents, and plants begin to
take hold across the island.

Food

Seeds

Many seeds available

Insects

Many insects available

Flowers

Many nectar flowers available

Competition

Competition has been reduced temporarily. Cohabitating populations
like the lowland and alpine pollenpeeper species have become more distinct from one
another, specializing to a point where the overlap between them is reduced.